Energetic costs of catch and release angling in Brook Trout (Salvelinus fontinalis) at two temperatures

Catch and release (C&R) angling is a common practice in recreational fisheries, which can involve a range of acute stressors for fish that lead to physiological and behavioural impairments. Following a C&R event, energy is expended to fuel recovery, while a cessation in feeding can limit energy intake. While the physiological and behavioural consequences of C&R have been extensively studied, the extent of the bioenergetic impacts has rarely been characterized. This study aimed to assess the energetic impacts of C&R stressors on Brook Trout (Salvelinus fontinalis)-a cold-water salmonid sensitive to temperature perturbations and air exposure. Adult Brook Trout were subjected to simulated angling events (i.e. 30s chase, 30s chase and 10s air exposure) or served as controls at 10°C and 15°C. Respirometry was used to measure energy expenditure through excess post-exercise oxygen consumption (EPOC), while a feeding experiment determined the time to return to feeding. Energy expenditure and reductions in energy consumption were incorporated into a bioenergetics model to predict growth outcomes following captures (i.e. 1, 3, 5) over 30 days. The stressors simulated here resulted in a maximum growth deviation of 4.1% (95% CI [2.8-6.5]) after a single capture and 21.0% (95% CI [14.6-33.4]) after five captures. Across temperatures, Brook Trout experienced higher peak metabolic rates at 15°C, but rapid recovery resulted in similar energetic costs of recovery to 10°C. However, our bioenergetic simulations revealed that prolonged (24 h) elevated daily temperature (15°C) occupancy raised metabolic energy expenditure negating the benefits of a faster resumption of feeding. Nevertheless, the moderate simulated C&R stressors tested here within the optimal temperature range of Brook Trout resulted in relatively small energetic consequences, even with numerous simulated captures. Future research should explore the bioenergetic effects of more intense (but still reasonably common) C&R stressors, including longer air exposure periods, hooking injuries and temperature extremes.